olymmath

Putnam 2023 B5

  • Session B

Determine which positive integers nn have the following property: For all integers mm that are relatively prime to nn, there exists a permutation π ⁣:{1,2,…,n}→{1,2,…,n}\pi\colon \{1,2,\dots,n\} \to \{1,2,\dots,n\} such that π(π(k))≡mk(modn)\pi(\pi(k)) \equiv mk \pmod{n} for all k∈{1,2,…,n}k \in \{1,2,\dots,n\}.

Curated text Kedlaya Putnam archive. Quoted with source.

Solutions

Human solution Solution 1 by Manjul Bhargava, Kiran Kedlaya and Lenny Ng

The terms of the source let olymmath link to this solution but not copy it. Read the solution (Kedlaya Putnam archive).

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